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Papers by Petrus Le Roux

Bulletin of Volcanology, 2020

New stratigraphic, lithological and petrographic analyses of La Poruña scoria cone (21° 53′ S-68°... more New stratigraphic, lithological and petrographic analyses of La Poruña scoria cone (21° 53′ S-68° 30′ W, Central Andes, northern Chile) allow the reconstruction of the eruptive sequence of this monogenetic cone. Petrographic and lithological characteristics allow us to identify three main lithostratigraphic units at La Poruña scoria cone. The first unit consists of agglutinated lapilli, spatter beds, and clastogenic lavas that are related to the construction of the cone. The other two units are associated with a lava flow field and consist of flow of andesitic composition, which differ both in their degree of weathering and in their development of channel, surface, and internal structures (e.g., levées, ogives, and joints). With these lithostratigraphic analyses, we interpret that the construction of La Poruña occurred during four main eruption phases involving Strombolian, Hawaiian, and transitional eruptive styles. Furthermore, differences in the degree of erosion, alteration, and weathering of the lithostratigraphic units in the lava field of La Poruña suggest that this flow field was formed during two eruptive events. The excellent outcrop conditions and preservation state of the volcanic products of La Poruña allow new stratigraphic insights that advance the wider and more general understanding and the dynamics of this important type of volcanism and the potential hazards of a scoria cone eruption. The polycyclic style of the eruption needs to be included in the hazards assessment of these centers type, especially when the cone is associated with structures that can be reactivated. This process could correspond to a second phase of activity, involving ash fall, bomb, and lava emission.

Numerous NW-SE trending dykes outcrop in south west of Jiroft, Southern Iran. These dykes are mai... more Numerous NW-SE trending dykes outcrop in south west of Jiroft, Southern Iran. These dykes are mainly composed of diorite, quartz diorite, gabbro-diorite, and gabbro. Plagioclases in the dyke swarm have composition ranging from An99.5Ab0.5 in cores, to An17Ab78Or5 in rims, and compositional variation with En42-49Wo39-40Fs11-18 in clinopyroxene plots across the augite field boundary. These rocks show strongly met-aluminous signatures and tholeiitic affinity. Studied rocks display LaN/LuN=0.68-2.19 and EuN/Eu*=1.63-1.92 with nearly flat heavy rare earth element (HREE). The U-Pb age dating of zircons from a dyke yielded 36.07±0.07 Ma indicating Eocene crystallization age, to an age of 783.85±1.98 Ma, indicating this dyke has zircon xenocrysts inherited. The initial 87Sr/86Sr and 143Nd/144Nd isotopic composition of studied swarm dykes are 0.705287±0.000009 and 0.512833±0.00001 respectively. Geochemical data show transitional geochemical characteristics between normal mid-ocean ridge basa...

Human isotopic ecology at its core aims to study humans as a part of their environments, as anima... more Human isotopic ecology at its core aims to study humans as a part of their environments, as animals within an ecosystem. We are complex animals with complicated foodways and mobility patterns which are hard to address without large multi-faceted datasets. As biomolecular data from archaeological remains proliferates scientists are now at the stage where we are able to collate large bodies of data and undertake complex meta-analyses and address the complexities of human ecology and past socio-environmental dynamics. Here we present a dataset of 862 entries of new primary isotopic data (37 faunal bone, 235 human enamel carbonate with a subset of 18 for 87/86Sr, 347 human bone, 243 human bulk dentine) within a larger dataset compiled from available legacy data. It contains a total of 8910 isotopic entries from ancient humans and animals relating to diet and mobility from the late Roman period into the Middle Ages (c. 400-1200 AD). It includes carbon, nitrogen, oxygen and strontium isot...

Journal of Volcanology and Geothermal Research, 2022

Nature Communications, 2021

Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the ov... more Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) δ18O values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30 km at Merapi to ≤20 km at Agung. Here we show that mean clinopyroxene δ18O values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt δ18O values of 5.7 ‰ (±0.2 1 SD) indistinguishable from the δ18O range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduc...

The Geology of the Arabian-Nubian Shield, 2021

Frontiers in Ecology and Evolution, 2021

The Andes are a unique geological and biogeographic feature of South America. From the perspectiv... more The Andes are a unique geological and biogeographic feature of South America. From the perspective of human geography, this mountain range provides ready access to highly diverse altitudinally arranged ecosystems. The combination of a geologically and ecologically diverse landscape provides an exceptional context to explore the potential of strontium isotopes to track the movements of people and the conveyance of material culture. Here we develop an isotopic landscape of bioavailable strontium (87Sr/86Sr) that is applied to reconstruct human paleogeography across time in the southern Andes of Argentina and Chile (31°–34°S). These results come from a macro-regional sampling of rodents (N = 65) and plants (N = 26) from modern and archeological contexts. This “Southern Andean Strontium Transect” extends over 350 km across the Andes, encompassing the main geological provinces between the Pacific coast (Chile) and the eastern lowlands (Argentina). We follow a recently developed approach ...

Scientific Reports, 2020

We present isotopic and morphometric evidence suggesting the migration of farmers in the southern... more We present isotopic and morphometric evidence suggesting the migration of farmers in the southern Andes in the period AD 1270–1420, leading up to the Inka conquest occurring ~ AD 1400. This is based on the interdisciplinary study of human remains from archaeological cemeteries in the Andean Uspallata Valley (Argentina), located in the southern frontier of the Inka Empire. The studied samples span AD 800–1500, encompassing the highly dynamic Late Intermediate Period and culminating with the imperial expansion. Our research combines a macro-regional study of human paleomobility and migration based on a new strontium isoscape across the Andes that allows identifying locals and migrants, a geometric morphometric analysis of cranio-facial morphology suggesting separate ancestral lineages, and a paleodietary reconstruction based on stable isotopes showing that the migrants had diets exceptionally high in C4 plants and largely based on maize agriculture. Significantly, this migration influ...

Gondwana Research, 2020

Abstract Felsic to intermediate igneous rocks from the Cuchilla Dionisio (or Punta del Este) Terr... more Abstract Felsic to intermediate igneous rocks from the Cuchilla Dionisio (or Punta del Este) Terrane (CDT) in Uruguay and the Varzea do Capivarita Complex (VCC) in southern Brazil were emplaced in the Tonian and experienced high-grade metamorphism towards the end of the Cryogenian. Geological and geochemical data indicate an S-type origin and formation in a continental within-plate setting by recycling of lower crustal material that was initially extracted from the mantle in the Palaeoproterozoic. Similar felsic igneous rocks of Tonian age occur in the Richtersveld Igneous Complex and the Vredefontein and Rosh Pinah formations in westernmost South Africa and southern Namibia and have been correlated with their supposed equivalents in Uruguay and Brazil. Geochemical and isotope data of the largely unmetamorphosed felsic igneous rocks in southwestern Africa imply a within-plate origin and formation by partial melting or fractional crystallization of mafic rocks that were extracted from the mantle in the Proterozoic. The parental melts of all of these Tonian igneous rocks from South America and southwestern Africa formed in an anorogenic continental setting at the western margin of the Kalahari Craton and were emplaced in, and/or contaminated by, Namaqua Province-type basement after separation from their source region. However, the source regions and the time of extractions thereof are different and, moreover, occurred at different palaeogeographical latitudes. New petrological data of CDT high-grade gneiss indicate a geothermal gradient of c. 20–25 °C/km, implying continental collisional tectonics following subduction and ocean basin closure at an active continental margin at the eastern edge of present-day South America in the late Cryogenian to early Ediacaran. The associated suture may be traced by the high-grade gneiss and amphibolite-facies mafic rocks in the CDT and probably continues northwards to the Arroio Grande Complex and the VCC in southern Brazil.

Archaeological and Anthropological Sciences, 2018

Precambrian Research, 2016

Quaternary International, 2017

Abstract The use of isotopic analysis in human and animal remains from the Holocene has proved to... more Abstract The use of isotopic analysis in human and animal remains from the Holocene has proved to be a very useful tool to explore the exploitation and adaptation of past populations to different environments. In this study we present isotopic analysis results of carbon, nitrogen and strontium from the Late Neolithic-Chalcolithic site of San Juan cave (Loarre, Spain). We analysed 33 humans, divided in adult and subadult groups, and 16 animals recovered from the same archaeological context. Stable isotope analysis of carbon and nitrogen has allowed to distinguish an homogeneous subsistence pattern during the Late Neolithic-Chalcolithic transition. The use of strontium isotopes ( 87 Sr/ 86 Sr) in human dental enamel suggests 19% (4 out of 21) are non-local individuals, based on comparison with the local bioavailable 87 Sr/ 86 Sr range calculated using microfauna teeth from the archaeological context, modern plants and snails. This new study gives information about Late Neolithic communities located in the north-east of the Iberian Peninsula, and it allows inference of the socio-economic structure, territorial mobility and individual provenance of humans.

Quaternary International, 2017

Abstract There are few carbon and nitrogen isotope ratio studies for prehistoric periods in the n... more Abstract There are few carbon and nitrogen isotope ratio studies for prehistoric periods in the northern part of the Iberian Peninsula, none of strontium isotopes. While most of the questions so-far addressed have been concerned with the transition to farming, the transition to social complexity has been greatly ignored even if multi-isotope studies could shed new light on internal socioeconomical dynamics during the emergence of complex societies in the region. The present study analyses a total of 67 archaeological samples (28 from human bones, 13 from animal bones and 26 from human tooth enamel) obtained from the deposits at Santimamine (Kortezubi, Bizkaia) and Pico Ramos (Muskiz, Bizkaia) dated to the Mesolithic, Late-Neolithic and Chalcolithic periods, and samples from different geological areas to characterize the bioavailable strontium of the region. These analyses provide new data about the diet on the coast of the Basque Country, confirming that the consumption of seafood was irrelevant already during the later stages of the Neolithic. The first 87 Sr/ 86 Sr analyses suggest the possibility of migration movements from other parts of Northern Iberia (i.e. Navarra) to the sites being studied.

Journal of Petrology, 2016

African Archaeological Review, 2016

Quaternary Science Reviews, 2016

Palaeogeography, Palaeoclimatology, Palaeoecology, 2014

Earth and Planetary Science Letters, 2002

Contributions to Mineralogy and Petrology, 2002

Bulletin of Volcanology, 2020

New stratigraphic, lithological and petrographic analyses of La Poruña scoria cone (21° 53′ S-68°... more New stratigraphic, lithological and petrographic analyses of La Poruña scoria cone (21° 53′ S-68° 30′ W, Central Andes, northern Chile) allow the reconstruction of the eruptive sequence of this monogenetic cone. Petrographic and lithological characteristics allow us to identify three main lithostratigraphic units at La Poruña scoria cone. The first unit consists of agglutinated lapilli, spatter beds, and clastogenic lavas that are related to the construction of the cone. The other two units are associated with a lava flow field and consist of flow of andesitic composition, which differ both in their degree of weathering and in their development of channel, surface, and internal structures (e.g., levées, ogives, and joints). With these lithostratigraphic analyses, we interpret that the construction of La Poruña occurred during four main eruption phases involving Strombolian, Hawaiian, and transitional eruptive styles. Furthermore, differences in the degree of erosion, alteration, and weathering of the lithostratigraphic units in the lava field of La Poruña suggest that this flow field was formed during two eruptive events. The excellent outcrop conditions and preservation state of the volcanic products of La Poruña allow new stratigraphic insights that advance the wider and more general understanding and the dynamics of this important type of volcanism and the potential hazards of a scoria cone eruption. The polycyclic style of the eruption needs to be included in the hazards assessment of these centers type, especially when the cone is associated with structures that can be reactivated. This process could correspond to a second phase of activity, involving ash fall, bomb, and lava emission.

Numerous NW-SE trending dykes outcrop in south west of Jiroft, Southern Iran. These dykes are mai... more Numerous NW-SE trending dykes outcrop in south west of Jiroft, Southern Iran. These dykes are mainly composed of diorite, quartz diorite, gabbro-diorite, and gabbro. Plagioclases in the dyke swarm have composition ranging from An99.5Ab0.5 in cores, to An17Ab78Or5 in rims, and compositional variation with En42-49Wo39-40Fs11-18 in clinopyroxene plots across the augite field boundary. These rocks show strongly met-aluminous signatures and tholeiitic affinity. Studied rocks display LaN/LuN=0.68-2.19 and EuN/Eu*=1.63-1.92 with nearly flat heavy rare earth element (HREE). The U-Pb age dating of zircons from a dyke yielded 36.07±0.07 Ma indicating Eocene crystallization age, to an age of 783.85±1.98 Ma, indicating this dyke has zircon xenocrysts inherited. The initial 87Sr/86Sr and 143Nd/144Nd isotopic composition of studied swarm dykes are 0.705287±0.000009 and 0.512833±0.00001 respectively. Geochemical data show transitional geochemical characteristics between normal mid-ocean ridge basa...

Human isotopic ecology at its core aims to study humans as a part of their environments, as anima... more Human isotopic ecology at its core aims to study humans as a part of their environments, as animals within an ecosystem. We are complex animals with complicated foodways and mobility patterns which are hard to address without large multi-faceted datasets. As biomolecular data from archaeological remains proliferates scientists are now at the stage where we are able to collate large bodies of data and undertake complex meta-analyses and address the complexities of human ecology and past socio-environmental dynamics. Here we present a dataset of 862 entries of new primary isotopic data (37 faunal bone, 235 human enamel carbonate with a subset of 18 for 87/86Sr, 347 human bone, 243 human bulk dentine) within a larger dataset compiled from available legacy data. It contains a total of 8910 isotopic entries from ancient humans and animals relating to diet and mobility from the late Roman period into the Middle Ages (c. 400-1200 AD). It includes carbon, nitrogen, oxygen and strontium isot...

Journal of Volcanology and Geothermal Research, 2022

Nature Communications, 2021

Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the ov... more Magma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) δ18O values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30 km at Merapi to ≤20 km at Agung. Here we show that mean clinopyroxene δ18O values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt δ18O values of 5.7 ‰ (±0.2 1 SD) indistinguishable from the δ18O range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduc...

The Geology of the Arabian-Nubian Shield, 2021

Frontiers in Ecology and Evolution, 2021

The Andes are a unique geological and biogeographic feature of South America. From the perspectiv... more The Andes are a unique geological and biogeographic feature of South America. From the perspective of human geography, this mountain range provides ready access to highly diverse altitudinally arranged ecosystems. The combination of a geologically and ecologically diverse landscape provides an exceptional context to explore the potential of strontium isotopes to track the movements of people and the conveyance of material culture. Here we develop an isotopic landscape of bioavailable strontium (87Sr/86Sr) that is applied to reconstruct human paleogeography across time in the southern Andes of Argentina and Chile (31°–34°S). These results come from a macro-regional sampling of rodents (N = 65) and plants (N = 26) from modern and archeological contexts. This “Southern Andean Strontium Transect” extends over 350 km across the Andes, encompassing the main geological provinces between the Pacific coast (Chile) and the eastern lowlands (Argentina). We follow a recently developed approach ...

Scientific Reports, 2020

We present isotopic and morphometric evidence suggesting the migration of farmers in the southern... more We present isotopic and morphometric evidence suggesting the migration of farmers in the southern Andes in the period AD 1270–1420, leading up to the Inka conquest occurring ~ AD 1400. This is based on the interdisciplinary study of human remains from archaeological cemeteries in the Andean Uspallata Valley (Argentina), located in the southern frontier of the Inka Empire. The studied samples span AD 800–1500, encompassing the highly dynamic Late Intermediate Period and culminating with the imperial expansion. Our research combines a macro-regional study of human paleomobility and migration based on a new strontium isoscape across the Andes that allows identifying locals and migrants, a geometric morphometric analysis of cranio-facial morphology suggesting separate ancestral lineages, and a paleodietary reconstruction based on stable isotopes showing that the migrants had diets exceptionally high in C4 plants and largely based on maize agriculture. Significantly, this migration influ...

Gondwana Research, 2020

Abstract Felsic to intermediate igneous rocks from the Cuchilla Dionisio (or Punta del Este) Terr... more Abstract Felsic to intermediate igneous rocks from the Cuchilla Dionisio (or Punta del Este) Terrane (CDT) in Uruguay and the Varzea do Capivarita Complex (VCC) in southern Brazil were emplaced in the Tonian and experienced high-grade metamorphism towards the end of the Cryogenian. Geological and geochemical data indicate an S-type origin and formation in a continental within-plate setting by recycling of lower crustal material that was initially extracted from the mantle in the Palaeoproterozoic. Similar felsic igneous rocks of Tonian age occur in the Richtersveld Igneous Complex and the Vredefontein and Rosh Pinah formations in westernmost South Africa and southern Namibia and have been correlated with their supposed equivalents in Uruguay and Brazil. Geochemical and isotope data of the largely unmetamorphosed felsic igneous rocks in southwestern Africa imply a within-plate origin and formation by partial melting or fractional crystallization of mafic rocks that were extracted from the mantle in the Proterozoic. The parental melts of all of these Tonian igneous rocks from South America and southwestern Africa formed in an anorogenic continental setting at the western margin of the Kalahari Craton and were emplaced in, and/or contaminated by, Namaqua Province-type basement after separation from their source region. However, the source regions and the time of extractions thereof are different and, moreover, occurred at different palaeogeographical latitudes. New petrological data of CDT high-grade gneiss indicate a geothermal gradient of c. 20–25 °C/km, implying continental collisional tectonics following subduction and ocean basin closure at an active continental margin at the eastern edge of present-day South America in the late Cryogenian to early Ediacaran. The associated suture may be traced by the high-grade gneiss and amphibolite-facies mafic rocks in the CDT and probably continues northwards to the Arroio Grande Complex and the VCC in southern Brazil.

Archaeological and Anthropological Sciences, 2018

Precambrian Research, 2016

Quaternary International, 2017

Abstract The use of isotopic analysis in human and animal remains from the Holocene has proved to... more Abstract The use of isotopic analysis in human and animal remains from the Holocene has proved to be a very useful tool to explore the exploitation and adaptation of past populations to different environments. In this study we present isotopic analysis results of carbon, nitrogen and strontium from the Late Neolithic-Chalcolithic site of San Juan cave (Loarre, Spain). We analysed 33 humans, divided in adult and subadult groups, and 16 animals recovered from the same archaeological context. Stable isotope analysis of carbon and nitrogen has allowed to distinguish an homogeneous subsistence pattern during the Late Neolithic-Chalcolithic transition. The use of strontium isotopes ( 87 Sr/ 86 Sr) in human dental enamel suggests 19% (4 out of 21) are non-local individuals, based on comparison with the local bioavailable 87 Sr/ 86 Sr range calculated using microfauna teeth from the archaeological context, modern plants and snails. This new study gives information about Late Neolithic communities located in the north-east of the Iberian Peninsula, and it allows inference of the socio-economic structure, territorial mobility and individual provenance of humans.

Quaternary International, 2017

Abstract There are few carbon and nitrogen isotope ratio studies for prehistoric periods in the n... more Abstract There are few carbon and nitrogen isotope ratio studies for prehistoric periods in the northern part of the Iberian Peninsula, none of strontium isotopes. While most of the questions so-far addressed have been concerned with the transition to farming, the transition to social complexity has been greatly ignored even if multi-isotope studies could shed new light on internal socioeconomical dynamics during the emergence of complex societies in the region. The present study analyses a total of 67 archaeological samples (28 from human bones, 13 from animal bones and 26 from human tooth enamel) obtained from the deposits at Santimamine (Kortezubi, Bizkaia) and Pico Ramos (Muskiz, Bizkaia) dated to the Mesolithic, Late-Neolithic and Chalcolithic periods, and samples from different geological areas to characterize the bioavailable strontium of the region. These analyses provide new data about the diet on the coast of the Basque Country, confirming that the consumption of seafood was irrelevant already during the later stages of the Neolithic. The first 87 Sr/ 86 Sr analyses suggest the possibility of migration movements from other parts of Northern Iberia (i.e. Navarra) to the sites being studied.

Journal of Petrology, 2016

African Archaeological Review, 2016

Quaternary Science Reviews, 2016

Palaeogeography, Palaeoclimatology, Palaeoecology, 2014

Earth and Planetary Science Letters, 2002

Contributions to Mineralogy and Petrology, 2002

An interim paper about the IDEMD project

Journal of Archaeological Sciences: Reports, 2019

Linear B administrative documents of the late second millennium BC from urban Knossos, Crete, rev... more Linear B administrative documents of the late second millennium BC from urban Knossos, Crete, reveal that spatially extensive and centrally monitored sheep flocks and wool production played a fundamental role in Mycenaean palatial economy. Here we employ multi-isotope (δ13C, δ18O, 87Sr/86Sr) analysis of sequentially sampled sheep and goat tooth enamel bioapatite to explore life histories of animals consumed at Knossos. Interpretation of isotopic results incorporates new baseline data on 87Sr/86Sr ratios of bioavailable Sr from modern Cretan plants collected in relevant zones. Results reveal a variety of herding regimes, including seasonal (‘wet/winter’ to ‘dry/summer’) vertical movement of sheep from lowland to highland locations, more restricted mobility for goats in lowland to mid-altitude territories, possible input of fodder to goat diet, and exploitation of a range of plant ecosystems. Results broadly match documentary evidence and ethnographic/ecological ex- pectations for sheep and goat herding at varying scales and underline the role of Knossos in mobilising resources from a range of herding systems and territories.

Scientific Reports, 2020

We present isotopic and morphometric evidence suggesting the migration of farmers in the southern... more We present isotopic and morphometric evidence suggesting the migration of farmers in the southern Andes in the period AD 1270-1420, leading up to the Inka conquest occurring ~ AD 1400. This is based on the interdisciplinary study of human remains from archaeological cemeteries in the Andean Uspallata Valley (Argentina), located in the southern frontier of the Inka Empire. The studied samples span AD 800-1500, encompassing the highly dynamic Late Intermediate Period and culminating with the imperial expansion. Our research combines a macro-regional study of human paleomobility and migration based on a new strontium isoscape across the Andes that allows identifying locals and migrants, a geometric morphometric analysis of cranio-facial morphology suggesting separate ancestral lineages, and a paleodietary reconstruction based on stable isotopes showing that the migrants had diets exceptionally high in C 4 plants and largely based on maize agriculture. Significantly, this migration influx occurred during a period of regional demographic increase and would have been part of a widespread period of change in settlement patterns and population movements that preceded the Inka expansion. These processes increased local social diversity and may have been subsequently utilized by the Inka to channel interaction with the local societies. Migrations are an intrinsic aspect of human societies in the present as in the past 1-3. While their dynamics differ 4,5 , migrations occurred across levels of socioeconomic complexity, from small-scale mobile societies to OPEN